Bone grinding is an essential procedure in neurological surgeries. Clinically, high-speed micro-grinding wheels are commonly used for removing pathological bones. However, high-speed grinding produces a lot of heat, resulting in bone necrosis and heat injury to surrounding tissues, and also has a certain impact on the coagulation function of the tissues, so that normal saline is usually used as cooling fluid to reduce the generation of the heat clinically. The temperature cannot be forecasted in grinding process, so the degree of heat injury cannot be controlled, and grinding heat injury has obtained clinically recognized concern. It is pointed out by Kondo et al. that in the flood cooling mode using normal saline, the maximum temperature generated by the grinding heat would still reach 43° C., and when the maximum temperature is higher than 43° C., optic nerves will be injured and blindness will be caused in serious cases. The maximum temperatures that different parts and different tissues of a human body can born are also different, for example, when the temperature is higher than a critical value 50° C., bones are subjected to different degrees of heat injury, and heat injury to the optic nerves occurs from 43° C. In relation to bone grinding, facial paralysis and femoral head necrosis are also common problems in neurological surgeries. Therefore, in bone grinding, the control of temperature is directly related to the success or failure of the surgeries.
At present, the most commonly used cooling mode in clinic is drip cooling, that is, normal saline is dripped onto a grinding area in a grinding process. When pathological bones needing to be removed by grinding are numerous and when lesions are at parts under wide views, flood cooling can be adopted, that is, a large amount of normal saline is sprayed onto the grinding area to improve the heat transfer capacity of the grinding area. In the machining field, the minimum quantity cooling (MQC) technology is the focus of the current research in grinding processing. However, MQC technology has the shortcoming of insufficient cooling performance, so that its application is greatly limited. A certain proportion of nanoparticles are added into MQC base fluid to improve the heat transfer capacity of a whole jet flow, and meanwhile, the nanoparticle jet minimum quantity cooling (Nano-MQC) for improving the lubrication effect of an oil film in the grinding area emerges. The so-called nanoparticle refers to an ultrafine tinny solid particle of which the size in at least one of the three dimensions is smaller than 100 nm. In Nano-MQC, nanoscale solid particles are added into the grinding fluid, and the nanoparticles, lubricating fluid and compressed air are jetted into the grinding area after mixing and atomization to carry out cooling and lubricating. Based on the solid enhanced heat transfer theory and by means of the advantage that the heat conductivity coefficients of solid particles are much greater than those of fluid and gas, in the same particle volume content, the superficial areas and thermal capacity of the nanoparticles are much greater than those of the millimeter or micron-sized solid particles, and thus the thermal conductivity of nanofluid formed by mixing the nanoparticles with the grinding fluid will be greatly improved.
MQC and Nano-MQC both require special nozzles to atomize cooling fluid or nanofluid, and the traditional atomizing nozzle is a pneumatic atomizing nozzle, that is, the compressed air is fully mixed the cooling fluid or the nanofluid by a gas path and a fluid path so as to be jetted to the grinding area from an outlet of the nozzle in the form of atomized droplets. However, the atomizing effect of the pneumatic atomizing nozzle is not good enough, and the droplets jetted out from the nozzle randomly float in the surrounding air. Jia et al. analyze the advantages and disadvantages of the traditional pneumatic atomizing nozzle, and invent an electrostatic atomizing nozzle, which further atomizes the compressed air and the cooling fluid or the nanofluid on the basis of pneumatic atomization by using the electrostatic atomizing principle, and meanwhile charges the ejected droplets by using the electrostatic charge principle, the charged droplets directionally move towards a workpiece under the action of an electric field force, and thus droplet distribution can be controlled.
Due to high speed rotation of a grinding tool in a bone grinding process, a gas flow barrier hinders the grinding fluid from entering the grinding area effectively. In the drip cooling and the flood cooling, effective cooling fluid capable of entering the grinding area is very little, and the effective flow rates of the MQC and Nano-MQC are very non-ideal. The emergence of the phase change heat transfer technology brings hope for the development of small low-temperature medical equipment. A phase change heat transfer type grinding head consisting of a hollow shaft can be divided into an evaporation segment, a heat insulation segment and a condensation segment, and has a hollow cavity having an initial vacuum degree therein and being filled with a proper amount of working fluid. When the rotating speed is high enough, the working fluid rotates with the grinding head and covers an inner wall surface of the hollow cavity in the grinding head to form an annular fluid film. The grinding area is heated when the grinding head is working, so the working fluid in the grinding area will be evaporated, the fluid film becomes thinner, and the generated steam will flow to the other end of the grinding head. The steam releases heat at the condensation segment to condense into fluid, so that the fluid film is thickened. The condensate returns to a heating end along the inner wall surface under the action of a component force of a centrifugal force. By means of such continuous evaporation, steam flow, condensation and fluid reflux, the heat is transferred from the heating end to the condensation segment. Chen et al. verified the design feasibility and the heat transfer effect of the phase change heat transfer type grinding head by evaluating the isothermal performance, the starting performance and the self heat transfer capacity of the phase change heat transfer type grinding head.
The performance of abrasive grains on the grinding head also has a great impact on the grinding temperature. In order to suppress the heat generated in the grinding area, Toshiyuki carries out grinding experiments on a bovine femur by using an ordinary diamond grinding head, a SiO2 adhered diamond grinding head and a TiO2 adhered diamond grinding head, and finds that compared with the ordinary diamond grinding head, the SiO2 adhered diamond grinding head can slightly reduce the grinding temperature and the grinding torque at the beginning of the grinding, then the grinding temperature exceeds a threshold after a certain period of time, and the same surface load occurs in the grinding like the ordinary diamond grinding head. However, due to the hydrophilicity of micron-sized TiO2 particles, the grinding temperature of the TiO2 adhered diamond grinding head is greatly reduced.
The internal cooling mode is also a common cooling mode in drilling and mechanical grinding processing. In the internal cooling mode, the cooling fluid is directly conveyed to a cutting area through an internal cooling hole of a drill bit or a grinding wheel, so as to effectively reduce the cutting temperature.
Upon research, patent No. ZL201310277636.6 relates to an automatic adjustment type mechanical arm grinding clamping device with six degrees of freedom for medical surgeries, disclosing a technology that has high control accuracy and can effectively avoid the mechanical injury to brain tissues. The mechanical arm grinding clamping device has three rotation and three movement degrees of freedom, namely six degrees of freedom in total, thereby realizing skull surgery operations of arbitrary poses and solve the problems of large working space, high operation difficulty, low operation efficiency and unnecessary additional injury to patients of the traditional handheld operation devices. The device is mainly operated by advanced surgical instruments, and by virtue of the automatic adjustment mechanical arm with six degrees of freedom and the clamping device installed at a front end of the mechanical arm, the device has obvious advantages in aspects of treatment effect, pain reliving ability, recovery period, medical cost and the like. However, the device is not provided with a grinding temperature detection device, so that temperature change in the grinding process cannot be controlled.
Patent No. ZL201310030327.9 relates to an online surgery skull grinding temperature detection and controllable hand-held grinding device, disclosing a technology that monitors an acoustic emission signal of bone grinding to adjust the rotating speed of a grinding wheel and reduce the grinding temperature in the bone grinding process so as to effectively avoid the heat injury to brain tissues. An acoustic emission sensor is arranged at a joint of the grinding wheel and a housing, the acoustic emission signal detected by the acoustic emission sensor during the bone grinding is received by a signal analysis processing module to determine whether an overheating condition occurs, and the rotating speed of a DC motor is controlled by a feedback device. However, sound waves cannot penetrate through the bone tissue and have a significant loss when penetrating through gas-containing tissues, thereby influencing the curative effect. In addition, the device does not monitor the speed and the torque of the grinding wheel in real time, and cannot feed back and control the effective removal condition of pathological bones or the load born by the grinding wheel.
Patent No. ZL201420565334.9 relates to a skull surgery grinding experimental platform with multiple degrees of freedom, including a MQC system, a platform with three degrees of freedom, an electric spindle rotating device, an electric spindle, a grinding force measurement device and a grinding temperature measurement device. The grinding temperature is measured accurately by using three thermocouples distributed in steps, the grinding force is measured by a grinding dynamometer, and guidance is provided for clinical practice by analyzing experimental data. However, in clinical bone grinding surgeries, different surgical areas, different cooling fluid and cooling modes, and the sufficiency of operation experience of doctors will lead to actual and theoretical differences.
The existing invention or device does not consider the treatment on the wound after the bone grinding. When the lesion is located in a wider part, a manual binding mode can be adopted to prevent the infection of the wound. However, when the lesion is at a relatively complex position in the internal structure of human body, in a skull base brain tumor removal surgery for example, because of the complex structure of the skull base and the narrow surgery space, no effective mode is available to treat the wound after the surgery.